From: Halil Pasic <pasic@linux.ibm.com>
Date: Fri, 27 Aug 2021 14:54:29 +0200
Subject: KVM: s390: index kvm->arch.idle_mask by vcpu_idx
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: a3e03bc1368c1bc16e19b001fc96dc7430573cc8
Patch-mainline: v5.15-rc1
References: bsc#1190973

While in practice vcpu->vcpu_idx ==  vcpu->vcp_id is often true, it may
not always be, and we must not rely on this. Reason is that KVM decides
the vcpu_idx, userspace decides the vcpu_id, thus the two might not
match.

Currently kvm->arch.idle_mask is indexed by vcpu_id, which implies
that code like
for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) {
                vcpu = kvm_get_vcpu(kvm, vcpu_id);
		do_stuff(vcpu);
}
is not legit. Reason is that kvm_get_vcpu expects an vcpu_idx, not an
vcpu_id.  The trouble is, we do actually use kvm->arch.idle_mask like
this. To fix this problem we have two options. Either use
kvm_get_vcpu_by_id(vcpu_id), which would loop to find the right vcpu_id,
or switch to indexing via vcpu_idx. The latter is preferable for obvious
reasons.

Let us make switch from indexing kvm->arch.idle_mask by vcpu_id to
indexing it by vcpu_idx.  To keep gisa_int.kicked_mask indexed by the
same index as idle_mask lets make the same change for it as well.

Fixes: 1ee0bc559dc3 ("KVM: s390: get rid of local_int array")
Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Christian Bornträger <borntraeger@de.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: <stable@vger.kernel.org> # 3.15+
Link: https://lore.kernel.org/r/20210827125429.1912577-1-pasic@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[ ptesarik: Changes to vcpu_pre_run() and __airqs_kick_single_vcpu()
  have been omitted, because SLE12-SP5 does not contain upstream commit
  9f30f62163786a0b80e0886046b5c66e714e7e71 ]
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/include/asm/kvm_host.h |    1 +
 arch/s390/kvm/interrupt.c        |    4 ++--
 arch/s390/kvm/kvm-s390.h         |    2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -596,6 +596,7 @@ struct kvm_s390_float_interrupt {
 	struct kvm_s390_mchk_info mchk;
 	struct kvm_s390_ext_info srv_signal;
 	int next_rr_cpu;
+	/* indexed by vcpu_idx */
 	unsigned long idle_mask[BITS_TO_LONGS(KVM_MAX_VCPUS)];
 	struct mutex ais_lock;
 	u8 simm;
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -319,13 +319,13 @@ static unsigned long deliverable_irqs(st
 static void __set_cpu_idle(struct kvm_vcpu *vcpu)
 {
 	atomic_or(CPUSTAT_WAIT, &vcpu->arch.sie_block->cpuflags);
-	set_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	set_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static void __unset_cpu_idle(struct kvm_vcpu *vcpu)
 {
 	atomic_andnot(CPUSTAT_WAIT, &vcpu->arch.sie_block->cpuflags);
-	clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	clear_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static void __reset_intercept_indicators(struct kvm_vcpu *vcpu)
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -52,7 +52,7 @@ static inline int is_vcpu_stopped(struct
 
 static inline int is_vcpu_idle(struct kvm_vcpu *vcpu)
 {
-	return test_bit(vcpu->vcpu_id, vcpu->kvm->arch.float_int.idle_mask);
+	return test_bit(kvm_vcpu_get_idx(vcpu), vcpu->kvm->arch.float_int.idle_mask);
 }
 
 static inline int kvm_is_ucontrol(struct kvm *kvm)